Fractures of limb bones have been treated with internal fixation devices, such as plates lying on the surface of a bone, nails running inside the medullary canal of a fractured bone, and/or screws affixing both ends of a fractured bone together. These internal fixation devices may provide reasonable structural rigidity and/or stability to the fractured bone without compromising some of the strain desired to stimulate bone cells.
An intramedullary fixation method is a traditional procedure for treating long bone fractures, which involves affixing the bone fracture using intramedullary nails, without disturbing the periosteum of the bone. Such a method may be accomplished in a closed manner, and the fractured bone may be functionally used (including weight bearing) during healing. The surgical approach for insertion of intramedullary nails varies slightly for each bone and is well known in the field of orthopedics.
Some of the problems associated with conventional intramedullary fixation methods include lack of rotation stability (i.e., fractured bone segments connected by a nail can rotate relative to each other), lack of longitudinal stability (i.e., fractured bone segments connected by a nail can move relative to each other along an axis of the nail), collapse of the fracture site in some fracture types, and/or undesired backup of nails. In addition, intramedullary fixation methods may introduce interlocking screws across the nail, creating some disadvantages. Specifically, conventional intramedullary fixation nails for long bones may include a rigid structure (hollow or full) that may be locked at their extremes by the addition of screws transversally applied through the bone walls and the nail itself. This additional step generally makes the operation longer and more complicated, and may require additional skin incisions and/or longer use of an image intensifier (X-ray). Furthermore, undesired gaps between the bone ends may originate from the screws, which are permanent unless removed in a new operation. In contaminated fractures, metallic intramedullary nails may propagate contamination through the entire canal, despite attempts at cleaning the fracture site, which may lead to bone infection.